Optimality based repetitive controller design for track-following servo system of optical disk drives

Area of Science:

• Control Systems Engineering
• Mechatronics
• Optical Disk Drive Technology

Background:

• Optical disk drive servo systems face challenges from periodic disturbances due to disk eccentricity.
• Repetitive control is effective but limited by low-pass filter bandwidth, which is constrained by plant uncertainty and stability.
• Maximizing filter bandwidth is crucial for improving disturbance attenuation.

Purpose of the Study:

• To propose an optimality-based repetitive controller design for track-following servo systems.
• To address challenges posed by norm-bounded uncertainties in the system.
• To enhance the performance of repetitive controllers by increasing the low-pass filter bandwidth.

Main Methods:

• Embedding a lead compensator within the repetitive controller structure.
• Formulating and solving two optimization problems to determine optimal controller parameters.
• Utilizing an optimality-based design approach for enhanced performance.

Main Results:

• Significantly increased system gain at periodic signal harmonics.
• Greatly enhanced bandwidth of the low-pass filter in the repetitive controller.
• Demonstrated effectiveness through simulation and experimental validation.

Conclusions:

• The proposed optimality-based repetitive controller effectively improves track-following accuracy in optical disk drives.
• Embedding a lead compensator is a viable strategy to overcome limitations in traditional repetitive control.
• The method offers a robust solution for systems with norm-bounded uncertainties.